The present invention relates generally to the control of air borne particulate matter and, more particularly, to the containment and capture of dust laden air within large confined spaces, such as, for example, cargo holds in ships, barges, bulk silos, and the like.
In ship loading and unloading operations involving granular or powder-like bulk cargos, such as, for example, cement, phosphate, lime, to name a few, dust laden air escapes periodically from the cargo hold and may be blown considerable distances into the surrounding environment. Such fugitive dust creates serious air pollution problems in most urban port locations and must be abated if the enterprise is to continue in operation. The vast size of the cargo holds in ships and the variables created by their differing dimensional openings and the influence of crosswinds, cause problems for cargo terminals in providing any type of dependable dust abatement equipment to control this ever present problem. Various approaches have been proposed in an attempt to control certain specific dust problems during ship loading operations, such as in grain loading operations, by providing a vacuum within a discharge conduit in the ship's hold, or by surrounding the loading chuts as shown in U.S. Pat. Nos. 3,739,893 and 3,867,969, respectively. It is also known to enclose a rather small and well defined loading area adjacent a hopper through the use of air stream and dust collection suction devices, as depicted in U.S. Pat. Nos. 3,909,223 and 3,908,720. While these devices are said to be satisfactory in controlling localized dust problems occurring at a specific location, they are not suitable for the capture of dust laden air which may be escaping in other portions of the cargo hold. These prior systems prove futile in capturing fugitive dust in the large open areas, such as ship holds, because the influence of these conventional dust control systems is vary limited to those areas immediately adjacent to the pick-up points. Since the ship's hold areas must be free and clear of obstacles to allow unloading booms and equipment to operate, any hold covers or enclosures and/or multiple dust pick-up points, along with the required air capacity for practical dust capture at these points, is either not feasible or is uneconomical.